Andrews, Eliza, active 1798-1824. Chronicles of Dorsa #1

Princess Natasia is the eldest child of the Emperor Andreth, ruler of the Four Realms. If she was a boy, she'd be the unquestioned heir to the throne. But as a girl, her main duty in life is to marry someone her father can shape into his successor. Everything changes when an unknown, would-be assassin nearly takes Tasia's life. Unsure of whom he can trust, the Emperor realizes that his daughter might be his best option for an heir. For fans of epic fantasy...with an LGBTQ twist